There are too many things you can argue

First I am not an expert in HR; some of my friends making their living there though. So, please consider as some suggestions, rather than guidelines.

In a negociation like this, you can always find more things to argue, even if the other party thinking the numbers are final.

1. Whether there is bonus plan? Is there any signing bonus?

2. What about benefit plan? Can I get more vacation days? More match in 401K or other profit sharing plans? What about medical insurance or other insurance?

3. Is this feasible for me to work flexible hours/remotely from home?

4. Is this possible for me get an early evalution for a raise? or I expect a big jump even within a year, is this possible?

5. How is career path in your company? Can I change my title to another one?

All in all in negocaition, some people are "good" cops and some people are "bad" cops. For those very blunt bad cops, you do not have to worry and you do not need to fall into their trap. Usually, they give you very tough choice, like this case either accept a very low offer or not accept it at all.

This is not business, not professional at all! Business is all about communication and make comprise; so your strategy is to make things far more colorful rather than those bad guys black and white choice.

You guys need far more role play games before you getting into real negaciations. Just practice more.

Good Luck